Establish the following vector inequalities geometrically or otherwise :
(a) `|a+b|le|a|+|b|`
(b) `|a+b|ge||a|-|b||`
(c ) `|a-b|le|a|+|b|`
(d) `|a-b|ge||a|-|b||`
When does the equality sign above apply ?

Explanation

Hint : The sum (difference ) of any two sides of a trangle is never less third side . Equality holds for collinear vectors.